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Semenov [28]
2 years ago
12

A frictionless pendulum is made with a bob of mass 19.7 kg. The bob is held at height = 0.934 meter above the bottom of its traj

ectory, and then pushed forward with an initial speed of 2.93 m/s. What amount of mechanical energy does the bob have when it reaches the bottom?
96 J

136 J

265 J

180 J
Physics
1 answer:
Alika [10]2 years ago
4 0

Answer:

265 J

Explanation:

Energy=PE+KE=mgh+ 0.5mv^{2} where KE is kinetic energy, PE is potential energy, m is the mass of an object, v is the speed, h is the height and g is acceleration due to gravity.

Substituting 19.7 Kg for mass, 0.934 for h, 2.93 for v and 9.81 for g then

Energy=19.7(9.81*0.934+0.5*2.93^{2})=265.063303\approx 265 J

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An elevator supported by a single cable descends a shaft at a constant speed. The only forces acting on the elevator are the ten
VikaD [51]

Answer:

C. The net work done by the two forces is zero joules.

Explanation:

Work (W) is defined as the product of force F) by the distance (d)the body travels due to this force.  

W= F*d Formula ( 1)

The work is positive (W+) if the force has the same direction of movement of the object.  

The work is negative (W-) if the force has the opposite direction of the movement of the object.

The component of the force that performs work must be parallel to the displacement.  

Calculation of the forces

We apply Newton's second law:

∑F = m*a

∑F : algebraic sum of the forces in Newton (N)

m : mass in kilograms (kg)

a : acceleration in meters over second square (m/s²)

∑F = m*a  

a = 0 because the elevator moves at constant speed.

∑F=0

T-W = 0

T = W  

Calculation of work done by the forces

W₁ :  work done by the gravity= (+ W*d ) J

W₂ : work done by the tension force=( -T*d) J

Net work done by the two forces(W₁-W₂):

W₁= W₂ .because T = W  

W₁-W₂ =0

3 0
3 years ago
What is the magnitude of the impulse that would cause the 2-kg box to accelerate from 2 m/s to 5 m/s?
Law Incorporation [45]

6 J is the impulse caused by the change in velocity of 2 kg box from 2 m/s to 5 m/s.

Answer:

The magnitude of impulse is 6 J.

Explanation:

Impulse is the force acting on any object for a given time interval. As force is equal to the product of mass and acceleration and acceleration is the rate of change of velocity with time. Then the product of force with time interval will be equal to the product of mass with change in velocity.

F = m a = \frac{m(v-u)}{(t_{2}-t_{1}  )}

FΔt = mΔv

Impulse = FΔt=mΔv

As the mass of box is given as 2 kg and the velocity changes from 2 m/s to 5 m/s, then the impulse = 2 × (5-2) = 2 ×3 =6 J

So 6 J is the impulse caused by the change in velocity of 2 kg box from 2 m/s to 5 m/s.

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3 years ago
Why is it impossible to build a machine that produces more energy than it uses?
Irina18 [472]
Because then it could mess up the machine with to much energy
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3 years ago
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